The production and sale of various oxygenated compounds, such as ethers and in particular lower alcohols such as ethanol and isopropyl alcohol has been hindered by the presence of highly undesirable odors in the commercial products presently being produced. These undesirable odors have been found to be particularly intense and to have caused considerable difficulty in the marketing of these products, which presently have a wide variety of commercial uses. In particular, these commercial uses have included use as solvents, disinfectants, spray products, and in many areas where the presence of such odors is of extreme significance, particularly is cosmetics and medicinal formulations.
This problem is particularly significant with respect to the commercial production of isopropyl alcohol, which in view of its excellent solubility, low toxicity, and cost, has become widely used in such areas as cosmetic products, disinfectants, etc. There has thus been considerable need for commercial processes to deodorize these types of products without unnecessarily hindering the commercial production thereof. These efforts have generally been centered upon processes such as extractive distillation processes, use of ion exchange resins, adsorption on compounds such as activated charcoal, activated alumina, sand, and the like. In many of these cases the patentees have attempted to analyze the various possible causes of negative odor characteristics in these materials, such as in U.S. Pat. No. 2,729,682, assigned to the assignee of the present invention. In the latter patent, however, the patentee attempts to overcome the problems of "recycle" odor by incorporating into the propylene stream a C.sub.4 to C.sub.6 mono-olefin, followed by water extractive distillation.
In addition, U.S. Pat. No. 2,857,436 teaches the odor improvement of lower alcohols with successive passage of these materials through two different contact masses, a bed of unglazed porcelain and a bed of iron metal such as steel wool, so that the process is inherently uneconomic. The patentee also teaches that other metals such as copper, nickel and zinc have no effect.
None of these prior methods have, however, resulted in a commercially acceptable method for arriving at products having acceptable odor levels with economically and commercially acceptable utility.
Thus, for example, U.S. Pat. No. 2,356,689 teaches a method for the purification of such alcohols employing solid cuprous chloride in specified amounts to stabilize and improve the odor of these alcohols. This method is directed towards the removal of certain small quantities of odor causing impurities therefrom. In addition, this method employs the cuprous chloride as part of the alcohol finishing or purification procedure.
Furthermore, U.S. Pat. No. 2,663,745 discloses a process whereby the quality of various alcohols is improved by intimate contact with small sized glass particles, i.e., having particle sizes of between about 4 and 20 mesh.
In another area, not concerned with alcohols made by hydration methods but rather with oxo alcohols of higher molecular weight, C.sub.4 -C.sub.12, made by the hydroformylation of olefins followed by hydrogenation with sulfided catalysts, the patentee in U.S. Pat. No. 2,585,816 discloses the treatment of alcohols such as isooctanol of high sulfur content by metals such as mercury, copper and nickel, viz., Raney nickel or nickel on a support, essentially for reducing the sulfur content thereof, e.g. from 58-83 ppm to 10-27 ppm, thereby improving color. However, such treatment is not capable of deodorizing isooctanol to produce a pleasant smelling product, as demonstrated in Example 8 below.
In a more recent development, Japanese Pat. No. 51-1684 discloses another method for purifying isopropyl alcohol comprising contacting the alcohol with various Raney metals, including Raney nickel. This method includes contacting with the Raney metal, preferably in the presence of a reducing gas such as hydrogen. The Raney metals are present in amounts of from about 0.01 to 5 parts per hundred parts of alcohol. This procedure is not commercially feasible, however, particularly due to the fact that the Raney metals are extremely unstable and potentially dangerous to use.
The removal of odor from lower alcohols is difficult, inasmuch as the contaminants responsible are present in very small amounts and one doesn't know just which contaminants are causing the odor. Although the references cited date back to the early 50's, the problem of deodorizing isopropanol has persisted up to present times. Thus, the problem is a difficult one, the solution to which has a high degree of unpredictability so that this is an area where there is little obviousness.
The search has therefore continued for new methods for deodorizing lower alcohols, i.e.. C.sub.2 and C.sub.3 alcohols, such as isopropyl alcohol, and their ether and ester derivatives such as diethyl ether in a commercially acceptable and simple manner.